The invention concerns a method for manual control of the ratio of a continuously variable transmission (CVT).
The operating strategy of a continuously variable transmission (CVT) is usually aimed at good driveability, favorable fuel consumption and good smoothness during adjustment of the transmission ratio. Since the criteria for an operating strategy of a continuously variable transmission partly conflict, a compromise is usually made. In order to adapt the automated operating behavior of the continuously variable transmission to the driver""s wishes and environmental influences, adaptive driving strategies have become known.
The Applicant""s published patent application, DE-OS 196 00 915, e.g. describes a method of operating point control in an automatic operating mode in which the actual control of the operating point in a preset driving range, having a lower and an upper limit, is continuously updated by processing, without filtering, actual input signals essentially dependent on the manner of driving. Thus, the position of the operating point in the variogram of the transmission is continuously recalculated and mainly determined by the activities of the driver.
In all methods for automatic guidance of the operating point, it is disadvantageous that, in spite of elevated adaptation expenditure, not all the driver""s wishes can be complied with, especially the wish for possible manual engagement.
German Patent No. DE 41 20 540 proposes to provide, together with a first operating mode having automatic driving strategy, a second operating mode in which the driver can control by manual action the operating behavior of a multi-step transmission. For this purpose, a number of preset, constant ratios or ratio steps are stored, e.g. in a characteristic field. If the driver issues a manual shift command to the transmission, the constant transmission ratios are selected from the characteristic field depending on a driving conditions.
The production of a multi-step transmission with constant ratios and a manual operating strategy for a continuously variable transmission makes it possible for the driver, when preferred, to use performance-oriented engagement to select the transmission ratio.
The present invention is based on the problem of providing control of the ratio of a continuously variable transmission having an automatic operating mode and a second manual operating mode in which the operating behavior is improved in the manual operating mode in which the driver has direct control of the selection of the ratios.